A mechanical seal, an example of a slide component, is evaluated for its performance by a leakage rate, a wear rate, and a torque. In conventional arts, by optimizing the seal material and the sealing face roughness of mechanical seals, their performance is increased to achieve low leakage, long life, and low torque. However, due to growing awareness of environmental problems in recent years, a further improvement in the performance of mechanical seals has been demanded, for which technology development beyond the limits of the conventional arts has been required.
In that context, the present inventors have confirmed that in a mechanical seal of a water pump used for cooling a water-cooled engine, for example, an additive in LLC, a type of antifreeze, such as silicate or phosphate (hereinafter, referred to as a “deposit formation-causing substance”) can be concentrated on a sealing face, forming deposits as time passes, and degrading the function of the mechanical seal. The deposit formation is considered as a phenomenon that occurs likewise in mechanical seals of apparatuses that handle chemicals or oils.
There is a known conventional mechanical seal in which a sealing face is formed with grooves to form a fluid layer in order to prevent occurrence of wear or burn damage of sealing faces due to frictional heat generation (see Patent Documents 1, 2, and 3, for example). However, these inventions only introduce a fluid into a sealing face, and do not take measures to prevent formation of deposits on a sealing face.